Improved extraction of lipids from strawberry

Abstract

A high degree of variability in strawberry lipid content and fatty acid composition, previously observed after two extractions with chloroform-methanol-water following the Bligh and Dyer method, was reduced by extracting three times with larger volumes. The previously observed variation was caused by incomplete lipid extraction while the internal standard, methylheptadecanoate, was quantitatively extracted. The improved procedure caused by itself little variation in the lipid determination. The remaining variability was predominantly due to the heterogeneity of the strawberry population. Ripe fruit contained slightly more lipid than unripe fruit, and these lipids were richer in oleic acid and less rich in linoleic acid. The improved extraction procedure was however more cumbersome than three extractions with chloroform-methanol followed by evaporation to dryness and purification according to Bligh and Dyer in a small volume of chloroform-methanol-water. The latter procedure yielded a slightly larger amount of lipids and was more suitable to the analysis of a large number of small samples. In conclusion, equivalent extraction of internal standard and sample lipids should not be taken for granted.